The fines have been imposed by the U.K. Financial Services Authority and U.S. Commodity Futures Trading Commission.

Announcing its imposition of a £59.5m fine, the FSA says Barclays’ misconduct included:

making submissions which formed part of the LIBOR and EURIBOR setting process that took into account requests from Barclays’ interest rate derivatives traders. These traders were motivated by profit and sought to benefit Barclays’ trading positions;

seeking to influence the EURIBOR submissions of other banks contributing to the rate setting process; and

reducing its LIBOR submissions during the financial crisis as a result of senior management’s concerns over negative media comment.

In a statement Tracey McDermott, the FSA’s acting director of enforcement and financial crime, said: “Barclays’ misconduct was serious, widespread and extended over a number of years. The integrity of benchmark reference rates such as LIBOR and EURIBOR is of fundamental importance to both UK and international financial markets. Firms making submissions must not use those submissions as tools to promote their own interests.

“Making submissions to try to benefit trading positions is wholly unacceptable. This was possible because Barclays failed to ensure it had proper controls in place. Barclays’ behaviour threatened the integrity of the rates with the risk of serious harm to other market participants.”

“The FSA continues to pursue a number of other significant cross-border investigations in this area and the action we have taken against Barclays should leave firms in no doubt about the serious consequences of this type of failure.”

On Twitter Green Party London Assembly Member Jenny Jones backed calls for the bank to be dropped as the scheme’s sponsor while City Hall’s Liberal Democrats have suggested the fines make it necessary to “revisit” questions about the deal.

Barclays is the second Transport for London sponsor to face regulatory action in recent weeks.

Last month Wonga, which controversially sponsored TfL’s free New Year’s Eve travel in 2010, was reprimanded by the Office of Fair Trading for using “aggressive” and “misleading” debt collection methods.

The London Assembly has previously called on the Mayor to adopt “a code of ethics governing for future sponsorship and advertising deals” and for TfL to set out “how it would manage a situation where a sponsor suffered major reputational damage” after a sponsorship agreement was entered into.